Yes, most castor derivatives are largely bio-based, because most of their carbon comes from castor seed, a crop grown each year. But bio-based does not mean fully bio-based, biodegradable or low carbon, and each claim needs its own evidence.
Products such as hydrogenated castor oil, 12-HSA and sebacic acid keep the castor carbon chain, so their bio-based carbon share is usually high. Products that combine castor with petroleum-based materials, such as some polyols and esters, have a lower share.
How bio-based content is measured
Bio-based carbon is measured by radiocarbon analysis. Carbon from living plants contains carbon-14, while carbon from fossil sources has none. A lab compares the two to give the bio-based carbon share.
- ASTM D6866 is the method widely used in the US, including for the USDA BioPreferred programme.
- EN 16640 sets out the radiocarbon method for bio-based carbon content in Europe.
- EN 16785-1 goes further and calculates bio-based content by mass, counting oxygen, hydrogen and nitrogen as well as carbon.
What a test does and does not prove
If you plan to make a bio-based claim on your product, test the derivative you actually buy. Do not rely on a general statement from the supplier. Ask your customers or regulator which method they accept.
- It does not prove biodegradability, which needs its own tests, explained in what biodegradability testing is.
- It does not prove a low carbon footprint, because processing uses energy, hydrogen, methanol or caustic soda.
- It does not prove the crop was grown sustainably or without child labour.
- It does not cover chemicals added in processing, such as catalysts or petroleum-based co-reactants.
Sustainability claims
Buyers who need more than a bio-based figure sometimes ask for a life cycle assessment or for certification under a mass-balance or sustainable farming scheme. These schemes are product and supplier specific. Ask whether the plant holds the certificate itself, and check its scope and validity with the scheme's own register.
Green claims are regulated in many markets, including the EU and the UK. You are responsible for claims made on your own products, so check the rules with your legal or compliance adviser before you publish one. See also what certifications matter for castor derivatives.
Questions to ask the plant
- Which raw materials, other than castor oil, go into the product, and are any of them petroleum based?
- Has the plant had the product tested for bio-based carbon content, and by which method?
- Can it share the test report and the date of the test?
- Does it hold any sustainability certification for this product and this site?
Next step
We can collect a plant's sustainability documents, check them against the scheme registers and have lots tested by an independent lab. Book a free sourcing review to start.